Fuel cells are devices that directly convert chemical energy of reactants, i.e., fuel and oxidant, into direct current (DC) electricity. For an increasing number of applications, fuel cells are more efficient than conventional power generation, such as combustion of fossil fuel and more efficient than portable power storage, such as lithium-ion batteries.
In general, fuel cell technologies include a variety of different fuel cells, such as alkali fuel cells, polymer electrolyte fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells and enzyme fuel cells. Today's more important fuel cells can be divided into three general categories, namely fuel cells utilizing compressed hydrogen (H2) as fuel, proton exchange membrane (PEM) fuel cells that use methanol (CH3OH), sodium borohydride (NaBH4), hydrocarbons (such as butane) or other fuels reformed into hydrogen fuel, and PEM fuel cells that use methanol (CH3OH) fuel directly (“direct methanol fuel cells” or DMFC). Compressed hydrogen is generally kept under high pressure, and is therefore difficult to handle. Furthermore, large storage tanks are typically required, and cannot be made sufficiently small for consumer electronic devices. Conventional reformat fuel cells require reformers and other vaporization and auxiliary systems to convert fuels to hydrogen to react with oxidant in the fuel cell. Recent advances make reformer or reformat fuel cells promising for consumer electronic devices. DMFC, where methanol is reacted directly with oxidant in the fuel cell, is the simplest and potentially smallest fuel cell, and also has promising power application for consumer electronic devices.
DMFC for relatively larger applications typically comprises a fan or compressor to supply an oxidant, typically air or oxygen, to the cathode electrode, a pump to supply a water/methanol mixture to the anode electrode and a membrane electrode assembly (MEA). The MEA typically includes a cathode, a PEM and an anode. During operation, the water/methanol liquid fuel mixture is supplied directly to the anode, and the oxidant is supplied to the cathode. The chemical-electrical reaction at each electrode and the overall reaction for a direct methanol fuel cell are described as follows:
Reaction at the anode:CH3OH+H2O→CO2+6H++6e−
Reaction at the cathode:O2+4H++4e−→2H2O
The overall fuel cell reaction:CH3OH+1.5O2→CO2+2H2O
Due to the migration of the hydrogen ions (H+) through the PEM from the anode through the cathode and due to the inability of the free electrons (e−) to pass through the PEM, the electrons must flow through an external circuit, which produces an electrical current through the external circuit. The external circuit may be any useful consumer electronic devices, such as mobile or cell phones, calculators, personal digital assistants and laptop computers, among others. DMFC is discussed in U.S. Pat. Nos. 5,992,008 and 5,945,231, which are incorporated by reference in their entireties. Generally, the PEM is made from a polymer, such as Nafion® available from DuPont, which is a perfluorinated material having a thickness in the range of about 0.05 mm to about 0.50 mm, or other suitable membranes. The anode is typically made from a Teflonized carbon paper support with a thin layer of catalyst, such as platinum-ruthenium, deposited thereon. The cathode is typically a gas diffusion electrode in which platinum particles are bonded to one side of the membrane.
The cell reaction for a sodium borohydride reformer fuel cell is as follows:NaBH4(aqueous)+2H2O→(heat or catalyst)→4(H2)+(NaBO2)(aqueous)H2→2H++2e−(at the anode)2(2H++2e−)+O2→2H2O (at the cathode)Suitable catalysts include platinum and ruthenium, among other metals. The hydrogen fuel produced from reforming sodium borohydride is reacted in the fuel cell with an oxidant, such as O2, to create electricity (or a flow of electrons) and water byproduct. Sodium borate (NaBO2) byproduct is also produced by the reforming process. Sodium borohydride fuel cell is discussed in United States published patent application no. 2003/0082427, which is incorporated herein by reference.
The patent literature discloses a number of containers for consumable substances that include electronic memory components. United States patent application publication no. US 2002/0154815 A 1 discloses a variety of containers that may include read-only memories, programmable read-only memories, electronically erasable programmable read-only memories, non-volatile random access memories, volatile random access memories or other types of electronic memory. These electronic memory devices may be used to retain coded recycle, refurbishing and/or refilling instructions for the containers, as well as a record of the use of the containers. The containers may comprise liquid ink or powdered toner for a printer. Alternatively, the containers may comprise a fuel cell.
United States patent application publication nos. US 2003/0082416 A1 and 2003/0082426 A 1 disclose a system including a host device and a fuel cell apparatus with an information storage device. The host device may be for example a PDA powered by a fuel cell stack and a removable fuel cartridge. The fuel cartridge includes the information storage device, which may be a non-volatile serial EEPROM memory chip. The data stored on the chip can be related to fuel management data, safety information, and marketing and manufacturing information. The initial fuel level data can be write-protected while the current fuel level is defined by a decrementable data field.
Japanese publication no. JP2003049996 discloses a hydrogen cartridge that has a memory device, a controller and a communication interface. Japanese publication no. JP2002161997 discloses another hydrogen cartridge that has bar code printed thereon. The bar code contains identification information for the cartridge. International publication no. WO 03/012902A1 discloses unit fuel cells with bar codes printed on the individual cells.